1. Field of the Invention
The preset invention relates to an automatic parameter adjustment device having a function for adjusting a parameter corresponding to a processing condition of a machine tool.
2. Description of the Related Art
In the prior art, when controlling a machine tool, an automatic parameter adjustment device may be used for automatically adjusting a control gain or an acceleration/deceleration parameter. For example, JP H07-319506 A discloses an auto-tuning controller having a means for automatically adjusting a control parameter so that a measured cycle time is equal to a desired time. Further, JP H07-319506 A describes that the controller may have a rough adjustment mode and a fine adjustment mode, and the optimum mode may be selected depending on a status of an object to be controlled, etc.
In a machine tool, it is necessary to appropriately adjust the parameter of the acceleration/deceleration or the control gain of each drive axis of the machine tool, depending on the application or the shape of a workpiece to be processed. For example, the optimum value for each parameter is different, between when a cycle time (or a processing time) is more important than processing accuracy, and when the processing accuracy is more important than the cycle time to the contrary. In the conventional automatic parameter adjustment device, it is possible to adjust the control gain up to a limit gain so as to not generate an oscillation phenomenon or it is possible to determine the acceleration/deceleration parameter in which the processing time is minimized, whereas it is difficult to adjust the parameter in accordance with an actual processing condition.
For example, when an acceleration/deceleration time constant is increased in order to reduce the processing time, overshoot may occur at an inversion portion of the drive axis of the machine tool (i.e., a curved portion or a discontinuous portion on a program path), whereby the processing accuracy may be deteriorated. On the other hand, if the acceleration/deceleration time constant is sufficiently large, followability to a command may be improved at the inversion portion of the drive axis, whereby the processing accuracy can be improved. However, the processing time is extended in this case. As such, it is difficult to balance the processing time and the processing accuracy, and it is desirable to automatically adjust the parameter suitable for each processing condition.
In the auto-tuning controller disclosed in JP H07-319506 A, the rough adjustment mode and the fine adjustment mode can be alternatively used. However, it is difficult to equally weight the processing time and the processing accuracy, or quantitatively determine the degree of importance (for example, the processing time may be negligible, or the processing accuracy may be slightly more important than the processing time, etc.) when either the processing time or the processing accuracy is more important than the other.